The present invention relates to a path route retrieval method in a time division multiplexer network in which working path (or routine) data can be obtained instantly.
FIG. 4 shows an example of prior art time division multiplexer. This time division multiplexer comprises dual system terminal interfaces 100 and 200, the dual system transmission line interfaces 300 and 400, the time switch (TSW) 500 for time slot switching, and a controller 600 for controlling and monitoring the terminal interfaces 100 and 200, transmission line interfaces 300 and 400 and a time switch 500. In addition, the multiplexer accommodates dual system transmission lines 30 and 40 through which multiplexed signals are transmitted, and terminal lines 10 and 20 connected to the respective dual system terminal units.
The controller 600 includes communication means 70 for communication with the controllers of other stations (i.e., other time division multiplexers), and a time slot (TS) allotment data memory 80 having time slot allotment data describing the allotment of specific time slots (TS) of the terminal interfaces 100 and 200 and transmission line interfaces 300 and 400 to the transmission lines 30 and 40. The controller 600 thus can read data to and from the other stations.
In this time division multiplexer, the transmission line 30 is connected to the transmission interface 300, and the transmission line 40 is connected to the transmission line interface 400. Signals having been transmitted through the transmission line 30 are delivered through the transmission line interface 300 to the time switch 500. The time switch 500 switches time slots according to a setting which has been made preliminarily in the controller 600 and delivers the signal to the separate transmission line interface 400 or the terminal interface 100 or 200 according to the setting.
The transmission line 40 is connected to the transmission line interface 400, and the signal delivered from the time switch 500 is sent out to the transmission line 40. The terminal line 10 is connected to the terminal interface 100, and the signal delivered from the time switch 500 is transmitted to the terminal line 10. The terminal line 20 is connected to the terminal interface 200, and the signal delivered from the time switch 500 is transmitted to the terminal line 20.
Where three or more time division multiplexers or stations constitute a time division multiplexer network, the time slot allotment data memory 80 in one of the three multiplexers contains information for the other stations as nodes. The stored time slot allotment data stored, which describes the transfer of data from an interface to another in the network through the time switch 500 and by the allotment of specific time slots of the terminal interfaces 100 and 200 or the transmission line interfaces 300 and 400 to the transmission lines 30 and 40. The content of the time slot allotment data includes ID (identification) number for each path. The controller 600 controls the time switch 500 according to the time slot allotment data. When necessary, the controller can also inform the other nodes of any trouble or the like using the communication means 70, according to the path data corresponding to each of the transmission lines 30 and 40. While in these time division multiplexers the individual parts are dual systems, the present invention is also applicable to three or more systems with system parts.
Where a network is formed with three or more of the above time division multiplexers, each station has its own internal data, and a monitor (not shown) which monitors the whole network is disposed for a specific station.
Each time division multiplexer has its own internal data and does not have any data concerning a path relaying route for communication with multiplexers. However, the relaying route can be changed independently of the path-terminating station. This dictates illogical communication that it is possible to obtain path data only from the monitor when making route retrieval from a station not having any monitor or route retrieval from a particular relaying station.
Therefore, too long of a time period lapses when making a survey of possible paths bypassing a trouble spot in the network in spite of the fact that these operations should be done nearly instantaneously.
As techniques related to the bypassing measure in time division multiplexers, a relaying line selection system is disclosed in Japanese Laid-Open Patent Publication No. 3-38132, a bypassing retrieval system is disclosed in Japanese Laid-Open Patent Publication No. 4-152735, and a bypassing route setting system is disclosed in Japanese Laid-Open Patent Publication No. 4-337942. In the disclosed bypassing route setting system, although data of routes to adjacent nodes are provided, these data are link unit data in such bypassing route setting. Therefore, the system cannot be directly applied to the route retrieval of working path data in time division multiplexers.